JP5295339B2 - Zoom lens and imaging apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a compact-size zoom lens having high optical performance over an entire zoom range. <P>SOLUTION: A zoom lens includes, in order from an object side to an image side, a first lens group of positive refractive power, a second lens group of negative refractive power, a third lens group of positive refractive power, a fourth lens group of negative refractive power, and a fifth lens group of positive refractive power. While the second, third, and fifth lens groups move at the time of zooming, the first and fourth lens groups do not move for zooming. The third lens group is constituted by two positive lenses and one negative lens. When the focal distance of the fourth lens group is f4, the focal distance of the entire system at an wide angle end fw, the focal distance of the negative lens constituting the third lens group f3n, and the focal distance of the third lens group f3, the zoom lens satisfies conditions: 1.0&lt;¾f4¾/fw&lt;17.0 and 0.4&lt;¾f3n¾/f3&lt;1.0 <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a zoom lens suitable for a photographing apparatus such as a digital camera or a video camera using a solid-state image sensor.

  As a zoom lens for a digital camera or video camera using a solid-state imaging device, a lens system that is small in size and has a high zoom ratio is required. A positive lead type zoom lens in which the lens unit closest to the object side has a positive refractive power is easy to achieve a high zoom ratio, and is particularly often used for a zoom lens having a zoom ratio of 10 or more. As a positive lead type, the entire lens system is compact and has a high zoom ratio. A zoom lens with a five-group structure consisting of lens groups of positive, negative, positive, negative, and positive refractive power in order from the object side to the image side is known. It has been.

  Among these five-group zoom lenses, zoom lenses are known in which the first lens group and the fourth lens group are stationary during zooming (Patent Documents 1 to 4).

  Patent Documents 1, 3, and 4 disclose examples in which the third lens unit is moved monotonously to the object side during zooming from the wide-angle end to the telephoto end.

  Patent Document 2 discloses an example in which the third lens unit is not moved during zooming.

  Further, in the zoom lens having the above-described five-group configuration, a zoom lens that moves all the lens groups of the first to fifth lens groups during zooming is known (Patent Document 5).

JP-A-5-215967 JP 7-311341 A JP 2002-228931 A US Pat. No. 4,991,943 JP 2002-365547 A

  In recent years, as a zoom lens used in an image pickup apparatus such as a digital camera or a video camera, a small zoom lens having high optical performance and a short total lens length has been demanded as the image pickup element is narrowed.

  In particular, a zoom lens that satisfies these demands has a problem of reducing the effective diameter of the front lens (effective diameter of the first lens unit on the object side), which has a strong effect on the thickness of the camera, and reducing the size. It has become. In order to reduce the effective diameter of the front lens, it is possible to reduce the size of the entire lens system by increasing the refractive power of each lens group. However, with this method, it is difficult to maintain good optical performance over the entire zoom range with a small number of lenses.

  In addition, in the zoom lens having the above-described five-group configuration, there is a method of increasing the zoom ratio by moving the first lens group during zooming. However, this method has problems such as a complicated lens barrel mechanism and an actuator with a large torque.

  An object of the present invention is to provide a zoom lens having a small overall lens system and a high zoom ratio, and an imaging apparatus using the same.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative lens having a negative refractive power. The fourth lens group includes a fifth lens group having a positive refractive power, and the second lens group, the third lens group, and the fifth lens group move during zooming, and the first lens group and the fourth lens group move. The lens group is stationary for zooming,
The first lens group includes a cemented lens obtained by cementing a negative lens and a positive lens in order from the object side to the image side, and a positive lens.
The third lens group includes two positive lenses and one negative lens,
The focal length of the fourth lens group is f4, the focal length of the entire system at the wide angle end is fw, the focal length of the negative lens constituting the third lens group is f3n, and the focal length of the third lens group is f3. When
1.0 <| f4 | / fw <17.0
0.4 <| f3n | / f3 <1.0
It is characterized by satisfying the following conditions.

  According to the present invention, a small zoom lens with a high zoom ratio can be obtained.

Lens sectional view of Example 1 Aberration diagram at the wide-angle end of the numerical example corresponding to Example 1. Aberration diagram at the intermediate zoom position in the numerical value example corresponding to Example 1. Aberration diagram at the telephoto end of a numerical example corresponding to Example 1. Lens sectional view of Example 2 Aberration diagram at the wide-angle end of a numerical example corresponding to Example 2. Aberration diagram at the intermediate zoom position of the numerical example corresponding to Example 2 Aberration diagram at the telephoto end of a numerical example corresponding to Example 2. Lens sectional view of Example 3 Aberration diagram at the wide-angle end of the numerical value example corresponding to Example 3 Aberration diagram at the intermediate zoom position in the numerical value example corresponding to Example 3 Aberration diagram at the telephoto end of a numerical example corresponding to Example 3. Lens sectional view of Example 4 Aberration diagrams at the wide-angle end of the numerical value example corresponding to Example 4. Aberration diagram at the intermediate zoom position in the numerical value example corresponding to Example 4 Aberration diagram at the telephoto end of a numerical example corresponding to Example 4. Schematic diagram of main parts of an imaging apparatus of the present invention

[Example 1]
Embodiments of the zoom lens of the present invention and an image pickup apparatus having the same will be described below.

  FIGS. 1A, 1B, and 1C are sectional views of lenses at the wide-angle end (short focal length end), the intermediate zoom position, and the telephoto end (long focal length end) of the zoom lens according to Embodiment 1 of the present invention. It is. 2, 3 and 4 are aberration diagrams of the zoom lens of Example 1 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  5A, 5B, and 5C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 2 of the present invention. 6, 7, and 8 are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  FIGS. 9A, 9B, and 9C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 3 of the present invention. 10, 11 and 12 are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  13A, 13B, and 13C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the fourth exemplary embodiment of the present invention. FIGS. 14, 15, and 16 are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  FIG. 17 is a schematic diagram of a main part of a digital camera (imaging device) including the zoom lens of the present invention.

  The zoom lens of each embodiment is a photographic lens system used in an imaging apparatus. In the lens cross-sectional view, the left side is the object side (front) and the right side is the image side (rear). In the lens cross-sectional view, L1 is a first lens group having a positive refractive power (optical power = reciprocal of focal length), L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. , L4 is a fourth lens group having a negative refractive power, and L5 is a fifth lens group having a positive refractive power.

  SP is an aperture stop, which is located on the object side of the third lens unit L3 or in the third lens unit L3, and moves together with the third lens unit L3 during zooming.

  G is an optical block corresponding to an optical filter, a face plate, or the like. IP is the image side, and when used as a photographing optical system for a video camera or a digital still camera, when the camera is for a silver salt film on the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor. Corresponds to the film surface.

  In the aberration diagrams, Fno is the F number, d, g, C, and F are the d-line, g-line, C-line, and F-line of the Fraunhofer line in this order. ω represents a half field angle, and ΔM and ΔS represent a meridional image plane and a sagittal image plane.

  In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit (second lens unit) L2 is positioned at both ends of the range in which the mechanism can move on the optical axis.

  In the zoom lens of each embodiment, the second, third, and fifth lens groups L2, L3, and L5 are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end.

  Specifically, zooming is performed by moving the second lens unit L2 monotonously to the image side. The third lens unit L3 is moved while having a part of a convex locus on the object side.

  The fifth lens unit L5 is moved non-linearly so as to correct the change of the image point due to zooming.

  The first lens unit L1 and the fourth lens unit L4 do not move for zooming.

  Further, a rear focus type is employed in which the fifth lens unit L5 is moved on the optical axis for focusing.

  For example, focusing from an infinitely distant object to a close object at the telephoto end is performed by extending the fifth lens unit L5 forward, as indicated by a straight line 5c in FIG. In addition, a curved line 5a and a dotted line 5b, which are solid line movement trajectories of the fifth lens unit L5 shown in the figure, are zoomed from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at close distance, respectively. The movement locus | trajectory for correct | amending the image plane fluctuation | variation accompanying this is shown.

  As described above, the movement locus in zooming of the fifth lens unit L5 differs depending on the object distance.

  In each embodiment, all or part of the third lens unit L3 is moved so as to have a component in a direction perpendicular to the optical axis to correct image blur (fluctuation in image point position) when the entire optical system vibrates. ing. That is, vibration isolation is performed. As a result, image stabilization is effectively performed without adding a new optical member such as a variable apex angle prism or a lens group for image stabilization.

  In each embodiment, during zooming, the first lens unit L1 is fixed and the third lens unit L3 is moved.

  If the first lens unit L1 is not moved during zooming, the structure of the lens barrel can be made strong against external pressure.

  In particular, when the first lens unit L1 is moved as an electric zoom, an actuator with a large torque is required so as not to lose the pressure from the outside. Such an actuator often has problems in terms of miniaturization and noise reduction. In each of the embodiments, the first lens unit L1 is not moved during zooming, and the second lens unit L2 and subsequent lens units are moved so that only an actuator having a relatively small torque is used. As a result, the lens system is reduced in size and noise is reduced during zooming.

  Next, at the time of zooming, the front lens diameter is reduced by moving the third lens unit L3 along a locus convex toward the object side.

  If the third lens unit L3 is fixed, the effective diameter of the front lens is determined by the light beam at the zoom position. Therefore, if the distance between the first lens unit L1 and the aperture stop SP is shortened at an intermediate zoom position, the effective diameter of the front lens is reduced.

  Therefore, in each embodiment, the third lens unit L3 and the stop SP are moved together during zooming, and the distance between the third lens unit L3 and the first lens unit L1 is shortened (shortened) at an intermediate zoom position from the wide angle end. ) To reduce the effective diameter of the front lens.

  Further, in order to achieve a small size and a high zoom ratio, it is preferable to share the zooming action to the second lens group as much as possible. Therefore, in order to ensure the movement stroke associated with the zooming of the second lens unit L2, the third lens unit L3 is moved to the image side from the intermediate zoom position toward the telephoto end. As a result, the third lens unit L3 is moved along a convex locus toward the object side to reduce the effective diameter of the front lens and increase the zoom ratio.

  As a conventional zoom lens having a small zoom ratio and a high zoom ratio, a zoom lens having a four-group configuration including first, second, and fourth lens groups having positive, negative, positive, and positive refractive power in order from the object side to the image side is known. It has been.

  In contrast, each embodiment of the present invention has a five-group configuration including first to fifth lens units having positive, negative, positive, negative, and positive refractive powers in order from the object side to the image side.

  In particular, each embodiment is characterized by having a fourth lens unit L4 having a negative refractive power as compared with the conventional four-unit zoom lens.

  Compared with a zoom lens having a four-group configuration, the fourth lens unit L4 having a negative refractive power can increase the refractive power of the third lens unit L3 having a positive refractive power. As a result, the sensitivity of vibration reduction of the third lens unit L3 is increased, and vibration reduction is facilitated with a small amount of movement.

  As a result, the effective optical diameter of the third lens unit L3 is reduced, and the size reduction in the radial direction is facilitated.

  Also, the drive unit for vibration isolation can be reduced in size. Further, when the refractive power of the fourth lens unit L4 having negative refractive power is increased to some extent, the light beam incident on the fifth lens unit L5 can be made afocal. Thereby, the lateral magnification of the fifth lens unit L5 is reduced, and the focus sensitivity can be increased. As a result, the moving stroke of the fifth lens unit L5 is shortened, and aberration fluctuations during focusing are reduced.

  The zoom lens of each embodiment increases the refractive power of the first lens unit L1 and the second lens unit L2 in order to reduce the size of the entire lens system. This increases the secondary spectrum of axial chromatic aberration and lateral chromatic aberration in the first lens unit L1 on the telephoto side. On the other hand, in each embodiment, these secondary spectra are satisfactorily obtained by using a material having a low dispersion and a high partial dispersion ratio (above 70 or more) as the material of the positive lens constituting the cemented lens of the first lens unit L1. It is corrected.

  In the zoom lens of each embodiment, the aperture diameter of the stop SP is changed with zooming. Specifically, the aperture diameter is the largest at the wide-angle end, and the aperture diameter is smaller than this at the telephoto side from the intermediate zoom position. Thereby, on the telephoto side from the intermediate zoom position, the height of the off-axis light beam passing through the front lens is lowered to reduce the effective diameter of the front lens.

  The aperture stop SP is disposed on the object side of the third lens unit L3 or in the third lens unit L3. In this way, the distance between the second lens unit L2 and the third lens unit L3 is further reduced at the telephoto end, and the total lens length can be shortened. In addition, since the third lens unit L3 is telephotoly arranged with a gap between the positive lens 31 and the negative lens 32, space can be effectively used by arranging the aperture stop SP therebetween.

  In each embodiment, an optical filter or a lens unit having a small refractive power may be added to the object side of the first lens unit L1 or the image side of the fifth lens unit L5.

  A teleconverter lens, a wide converter lens, or the like may be disposed on the object side or the image side.

  Next, the lens configuration of each lens group will be described.

  The first lens unit L1 includes, in order from the object side to the image side, a cemented lens including a negative lens and a positive lens, and a positive lens. This makes it possible to satisfactorily correct axial chromatic aberration, lateral chromatic aberration, and spherical aberration while maintaining a high zoom ratio.

  The second lens unit L2 includes, in order from the object side to the image side, a negative meniscus lens having a concave surface on the image side, a biconcave negative lens, and a positive lens. In each embodiment, the positive lens is made of a high dispersion material (Abbe number of 20 or less), and the variation in chromatic aberration due to zooming is satisfactorily corrected with a small number of lenses.

  The third lens unit L3 includes, in order from the object side to the image side, a positive lens 31 having a convex surface on the object side, a negative meniscus lens 32 having a concave surface on the image side, and a positive lens 33 having a biconvex shape. By arranging the positive lens 31 and the negative lens 32 at a certain distance, the entire third lens unit L3 has a telephoto configuration. As a result, the distance between the principal points of the second lens unit L2 and the third lens unit L3 is shortened, and the overall length of the lens is shortened. When such a negative lens 32 is provided, positive distortion occurs on the lens surface, and this may increase the eccentric distortion during vibration isolation. In order to reduce the eccentric distortion at this time, the distortion generated in the entire third lens unit L3 may be reduced. In each embodiment, the positive lens 33 is disposed on the image plane side of the negative lens 32 to correct the distortion aberration in the third lens unit L3 while maintaining the telephoto configuration. As a result, the occurrence of decentration distortion that occurs when the third lens unit L3 is shifted to perform image stabilization is reduced.

  The fourth lens unit L4 includes one negative lens. In each embodiment, the fourth lens unit L4 does not move during zooming. As a result, the variation in chromatic aberration generated in the fourth lens unit L4 due to zooming is reduced, and in particular, it is not necessary to use an achromatic structure.

  If the refractive power of the fourth lens unit L4 is increased with a small number of lenses, spherical aberration occurs. At this time, the lens shape can be corrected with the aberration generated in the third lens unit L3.

  In each example, the spherical aberration is corrected on each surface so that the refractive power of the air lens formed by the final lens surface of the third lens unit L3 and the object-side lens surface of the fourth lens unit L4 is weakened to some extent. ing.

  Further, when the negative refractive power of the fourth lens unit L4 is increased, a pincushion type distortion aberration is generated on the image side lens surface. In this case, it is preferable to use a lens shape that corrects the aberration generated in the fifth lens unit L5.

  In each example, the refractive power of the air lens formed by the image-side lens surface of the fourth lens unit L4 and the most object-side lens surface of the fifth lens unit L5 is weakened to some extent, and distortion aberration is generated on each lens surface. It is corrected.

  The fifth lens unit L5 includes a cemented lens having a positive refractive power as a whole, which includes a positive lens and a negative lens. This suppresses fluctuations in chromatic aberration associated with correction of image point fluctuations accompanying zooming with a small number of lenses.

  With the above-described configuration, each embodiment achieves a compact zoom lens with a high zoom ratio. Furthermore, the effect corresponding to each conditional expression is obtained so as to satisfy one or more of the following conditional expressions.

  The focal lengths of the entire system at the wide-angle end and the telephoto end are denoted by fw and ft, respectively. The order of the lens groups in which j is counted from the object side to the image side is shown.

  The lateral magnifications of the second lens unit L2 at the wide-angle end and the telephoto end are β2w and β2t, respectively. The lateral magnifications of the third lens unit L3 at the wide-angle end and the telephoto end are β3w and β3t, respectively.

  The lateral magnifications at the telephoto end of the fourth lens unit L4 and the fifth lens unit L5 are β4t and β5t, respectively.

  The third lens unit L3 includes two positive lenses and one negative lens, and the focal length of the negative lens is f3n.

  The fourth lens unit L4 includes one negative lens, and the curvature radii of the object-side and image-side lens surfaces of the negative lens are R4a and R4b, respectively.

  The first lens unit L1 has a cemented lens composed of a positive lens and a negative lens. The Abbe number of the material of the positive lens constituting the cemented lens is νd1p, and the partial dispersion ratio is θgF1p.

  During zooming from the wide-angle end to the telephoto end, the third lens unit L3 moves so as to have a convex locus on the object side. At this time, the distance in the optical axis direction at the intermediate zoom position with respect to the wide-angle end of the third lens unit L3 is M3wm, and the distance in the optical axis direction at the telephoto end with respect to the wide-angle end of the third lens unit L3 is M3wt.

  The intermediate zoom position Za is a zoom position where the third lens unit L3 is located closest to the object side during zooming.

The partial dispersion ratio θgF is defined as NC, NF, and Ng when the refractive indexes of the C-line, F-line, and g-line are NC
θgF = (Ng−NF) / (NF−NC)
It is expressed by the following formula.

  The signs of the distances M3wm and M3wt are defined as minus when the object is located on the object side compared to the image side and plus when the object is located on the image side compared with the object side.

At this time,
1.0 <| f4 | / fw <17.0 (1)
-0.8 <M3wm / fw <-0.2 (2)
-0.40 <M3wt / fw <0.20 (3)
0.70 <(β2t / β2w) / (ft / fw) <2.00 (4)
0.01 <(β3t / β3w) / (ft / fw) <0.20 (5)
1.00 <(1-β3t) × β4t × β5t <2.00 (6)
0.4 <| f3n | / f3 <1.0 (7)
0.1 <(R4a + R4b) / (R4a−R4b) <8.0 (8)
−0.0016νd1p + 0.641 <θgF1p (9)
2.0 <f1 / fw <6.0 (10)
1.00 <| f2 | / fw <1.50 (11)
1.5 <f3 / fw <3.0 (12)
1.5 <f5 / fw <3.0 (13)
One or more of the following conditions are satisfied.

  In each embodiment, by satisfying each conditional expression, an effect corresponding to the conditional expression is obtained.

  Next, the technical meaning of each conditional expression will be described.

  Conditional expression (1) defines the focal length of the fourth lens unit L4, that is, the refractive power. If the lower limit of the conditional expression (1) is exceeded and the refractive power becomes too strong, the Petzval sum increases on the negative side and the occurrence of field curvature increases. If the number of constituent lenses of the fourth lens unit L4 is increased in order to reduce the Petzval sum, the total lens length increases, which is not good. If the upper limit of conditional expression (1) is exceeded and the refractive power is too weak, the effect of disposing the fourth lens unit L4 having a negative refractive power is weakened. Further, the radial direction of the third lens unit L3 increases due to the decrease in the vibration proof sensitivity of the third lens unit L3.

  In addition, the luminous flux emitted from the fourth lens unit L4 tends to be convergent light, which is not good because the focus sensitivity of the fifth lens unit L5 decreases and the movement stroke increases.

  Conditional expression (2) relates to the distance in the optical axis direction at the intermediate zoom position with respect to the wide angle end of the third lens unit L3, and here corresponds to the amount of movement from the wide angle end to the intermediate zoom position. If the lower limit is exceeded and the amount of movement toward the object side is too large, the axial chromatic aberration is excessively generated in the third lens unit L3 at the intermediate zoom position, and this can be corrected by other lens units. It becomes difficult. If the amount of movement toward the object side is too small beyond the upper limit of conditional expression (2), the effect of using the movement associated with zooming of the third lens unit L3 as a convex locus is weakened, and the front lens diameter increases. Not good.

  Conditional expression (3) defines the distance in the optical axis direction at the telephoto end with respect to the wide-angle end of the third lens unit L3. If the telephoto end position is larger than the wide-angle end and located on the object side beyond the lower limit, the distance between the first lens unit L1 and the third lens unit L3 at the wide-angle end is increased in order to ensure the movement stroke of the second lens unit L2. As a result, the front lens diameter increases.

  If the position of the telephoto end exceeds the upper limit of conditional expression (3) and is positioned on the image side larger than the wide-angle end, the third lens unit L3 and the fourth lens unit L4 do not interfere with each other at the telephoto end. It is necessary to widen the interval. This is not good because the effective diameter after the fourth lens unit L4 increases.

  Conditional expression (4) is an expression that prescribes the variable magnification sharing of the second lens unit L2. If the lower-limit variable magnification share of the second lens unit L2 is too small, the variable-magnification action of the third lens unit L3 or the fifth lens unit L5 must be greatly increased. In either case, the movement stroke is extremely increased and the total lens length is increased.

  If the conditional expression (4) exceeds 1, the zoom ratio in the synthesis system of the lens group after the second lens group L2 (the synthesis system from the third lens group L3 to the fifth lens group L5) is less than 1. Means that. If the upper limit of conditional expression (4) is exceeded, the zoom ratio of this synthesis system is much less than 1, so the second lens unit L2 must be zoomed more than necessary, and the entire system can scale efficiently. It becomes difficult. In this case, in order to obtain a desired zoom ratio, the movement amount of the second lens unit L2 becomes larger than necessary, and the total lens length increases. By satisfying conditional expression (4), the variable magnification sharing between the second lens unit L2 and the subsequent lens unit is optimized, and shortening of the total lens length and high zoom ratio are facilitated.

  Conditional expression (5) is an expression that defines the variable magnification sharing of the third lens unit L3. When the zoom ratio of the third lens unit L3 is significantly less than 1 and approaches zero, conditional expression (5) also approaches zero. If the value exceeds the lower limit and approaches zero, the zooming action of the second lens unit L2 or the fifth lens unit L5 must be strengthened. In either case, the movement stroke is extremely increased and the total lens length is increased.

  If the variable magnification sharing is too large exceeding the upper limit of conditional expression (5), the third lens unit L3 moves greatly toward the object side from the wide-angle end toward the telephoto end. If the amount of movement at this time increases, the distance between the first lens unit L1 and the third lens unit L3 at the wide-angle end must be increased. As a result, the effective diameters of the first lens unit L1 and the second lens unit L2 increase.

  It should be noted that satisfying conditional expressions (4) and (5) is more preferable because the variable power sharing of the subsequent lens group is optimized than the second lens group L2.

  Conditional expression (6) defines the anti-vibration sensitivity of the third lens unit L3. (1-β3t) × β4t × β5t represents the ratio of the amount of movement of the third lens unit L3 in the direction perpendicular to the optical axis and the amount of movement of the image point on the image plane generated thereby, and the larger the value, the smaller the movement. The image point can be moved by the amount.

  If the lower limit of conditional expression (6) is exceeded and the image stabilization sensitivity is too low, the movement stroke for image stabilization increases and the effective diameter of the third lens unit L3 increases. As a result, the outer diameters of the lenses constituting the third lens unit L3 are increased, which leads to an increase in the size of the lens holder and the vibration isolation mechanism. Further, when anti-vibration sensitivity is high, it is necessary to finely drive the third lens unit L3 when performing anti-vibration control. However, if the anti-vibration sensitivity is too high exceeding the upper limit, it is difficult to control with high accuracy. .

  Conditional expression (7) is an expression that defines the focal length, that is, refractive power of the negative lens constituting the third lens unit L3. If the lower limit of conditional expression (7) is exceeded and the refractive power is too strong, the Petzval sum will increase on the negative side and a lot of field curvature will occur.

  If the upper limit of conditional expression (7) is exceeded and the refractive power is too weak, the telephoto configuration formed by the immediately preceding positive lens will be weakened, the distance between the principal points of the second lens unit L2 and the third lens unit L3 will be shortened, and the total lens length will be reduced. It becomes difficult to shorten.

  Conditional expression (8) is an expression defining the lens form factor of one negative lens of the fourth lens unit L4. If the curvature of the lens surface on the object side is too strong beyond the lower limit, spherical aberration occurs on the over side, which is not good. If the conditional expression (8) exceeds 1, a meniscus shape with a concave surface facing the image side is obtained.

  If the upper limit of conditional expression (8) is exceeded and the degree of meniscus becomes too strong, the position of the front principal point of the fourth lens unit L4 will be too much on the image side, and it will be difficult to secure an air gap with the third lens unit L3.

  Conditional expression (9) defines the partial dispersion ratio of the material of the positive lens constituting the cemented lens of the first lens unit L1.

If the partial dispersion ratio θgF1p is too small with respect to the Abbe number νd1p beyond the lower limit of the conditional expression (9), correction of the secondary spectrum generated in the negative lens constituting the cemented lens becomes difficult, and axial chromatic aberration is particularly generated on the telephoto side. And the secondary spectrum in off-axis chromatic aberration increases.

  Conditional expression (10) defines the focal length, that is, the refractive power of the first lens unit L1. If the lower limit of conditional expression (1) is exceeded and the refractive power is too strong, a large amount of spherical aberration occurs on the telephoto side. If the upper limit of conditional expression (10) is exceeded and the refractive power is too weak, it is difficult to make the second lens unit L2 at the same zoom ratio at the intermediate zoom position. When the lateral magnification of the second lens unit L2 is made equal at the intermediate zoom position, the moving stroke of the fifth lens unit L5 for image point correction can be suppressed. If the upper limit of conditional expression (10) is exceeded, the moving stroke of the fifth lens unit L5 increases, which is not good.

  Conditional expression (11) defines the focal length, that is, the refractive power of the second lens unit L2. If the lower limit of conditional expression (11) is exceeded and the refracting power is too strong, the aberration fluctuation accompanying the zooming generated in the second lens group will increase.

  In particular, variations in spherical aberration, coma, and field curvature increase. If the refractive power is too weak beyond the upper limit of conditional expression (11), the movement stroke of the second lens unit L2 increases in order to obtain a desired zoom ratio, and the total lens length and front lens diameter increase.

  Conditional expression (12) defines the focal length, that is, the refractive power of the third lens unit L3. If the lower limit of conditional expression (12) is exceeded and the refractive power is too strong, aberration fluctuations increase when the third lens unit L3 is moved in the direction perpendicular to the optical axis for image stabilization.

  In particular, the occurrence of decentration coma and image plane tilt increases.

  If the upper limit of conditional expression (12) is exceeded and the refracting power is too weak, the stroke when moving the third lens unit L3 in the direction perpendicular to the optical axis is increased for image stabilization, so the radial direction of the third lens unit is large. It will turn.

  Conditional expression (13) defines the focal length, that is, the refractive power of the fifth lens unit L5. If the lower limit of conditional expression (13) is exceeded and the refractive power is too strong, it will be difficult to secure a back focus of a length necessary for inserting a filter or the like.

  If the upper limit of conditional expression (13) is exceeded and the refracting power is too weak, it is not good because the moving stroke increases for correction of focus variation accompanying focusing and focusing.

  More preferably, the numerical range of each conditional expression is set as follows.

1.5 <| f4 | / fw <16.0 (1a)
-0.7 <M3wm / fw <-0.2 (2a)
-0.35 <M3wt / fw <0.18 (3a)
0.75 <(β2t / β2w) / (ft / fw) <1.95 (4a)
0.03 <(β3t / β3w) / (ft / fw) <0.17 (5a)
1.15 <(1-β3t) × β4t × β5t <1.90 (6a)
0.5 <| f3n | / f3 <0.9 (7a)
0.2 <(R4a + R4b) / (R4a-R4b) <7.6 (8a)
3.0 <f1 / fw <5.0 (10a)
1.05 <| f2 | / fw <1.40 (11a)
1.7 <f3 / fw <2.7 (12a)
1.7 <f5 / fw <2.8 (13a)
As described above, according to each embodiment, the first lens unit L1 has a high zoom ratio of about 10 times with a configuration in which the first lens unit L1 is fixed during zooming, and the front lens effective diameter is reduced. A high-performance zoom lens can be obtained.

  Next, an embodiment of a digital still camera (imaging device) used as a photographing optical system of the zoom lens of the present invention will be described with reference to FIG.

  In FIG. 17, reference numeral 20 denotes a camera body, and 21 denotes a photographing optical system constituted by the zoom lens of the present invention. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body. A memory 23 records information corresponding to the subject image photoelectrically converted by the image sensor 22. Reference numeral 24 denotes a finder for observing a subject image formed on the solid-state image sensor 22, which includes a liquid crystal display panel or the like.

  As described above, by applying the zoom lens of the present invention to an image pickup device such as a digital still camera, an image pickup apparatus having high optical performance is realized.

  The numerical examples of the present invention are shown below. In each numerical example, i indicates the order of the surfaces from the object side, Ri is the radius of curvature of the lens surface, Di is the lens thickness and the air space between the i-th surface and the i + 1-th surface, Ni, ν i represents the refractive index and Abbe number for the d-line, respectively. The two surfaces closest to the image side are the planes of the optical block.

  B, C, D, and E are aspheric coefficients. The aspherical shape is when the displacement in the optical axis direction at the position of the height H from the optical axis is x with respect to the surface vertex.

It is represented by However, R is a radius of curvature and K is a conic constant.

  Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

<Numerical Example 1>
f = 6.65 to 64.60 Fno = 3.61 to 5.67 2ω = 53.5 ° to 5.9 °
R 1 = 34.046 D 1 = 1.30 N 1 = 1.805181 ν 1 = 25.4
R 2 = 21.362 D 2 = 4.00 N 2 = 1.496999 ν 2 = 81.5
R 3 = -222.504 D 3 = 0.10
R 4 = 19.848 D 4 = 2.40 N 3 = 1.603112 ν 3 = 60.6
R 5 = 54.761 D 5 = Variable
R 6 = 46.607 D 6 = 0.70 N 4 = 1.882997 ν 4 = 40.8
R 7 = 5.978 D 7 = 2.85
R 8 = -32.488 D 8 = 0.60 N 5 = 1.696797 ν 5 = 55.5
R 9 = 18.150 D 9 = 0.40
R10 = 10.973 D10 = 1.70 N 6 = 1.922860 ν 6 = 18.9
R11 = 29.933 D11 = variable
R12 = Aperture D12 = 1.50
R13 = 10.521 D13 = 2.00 N 7 = 1.693500 ν 7 = 53.2
R14 = -36.903 D14 = 3.46
R15 = 72.561 D15 = 0.60 N 8 = 1.846660 ν 8 = 23.9
R16 = 8.320 D16 = 0.27
R17 = 11.308 D17 = 2.10 N 9 = 1.603112 ν 9 = 60.6
R18 = -20.621 D18 = variable
R19 = -29.577 D19 = 0.70 N10 = 1.487490 ν10 = 70.2
R20 = 13.248 D20 = variable
R21 = 14.526 D21 = 2.90 N11 = 1.804000 ν11 = 46.6
R22 = -17.609 D22 = 0.60 N12 = 1.846660 ν12 = 23.9
R23 = -65.759 D23 = variable
R24 = ∞ D24 = 1.28 N13 = 1.516330 ν13 = 64.1
R25 = ∞

\ Focal length 6.65 19.43 64.60
Variable interval \
D 5 0.70 10.00 19.30
D11 20.08 7.53 1.48
D18 1.50 4.75 1.50
D20 5.92 3.67 9.26
D23 7.13 9.39 3.79

Aspheric coefficient
R14 k = -1.43239e + 02 B = -1.80347e-04 C = 1.55168e-05 D = -4.23854e-07
E = 0.00000e + 00

<Numerical Example 2>
f = 6.61 ～ 64.78 Fno = 3.60 ～ 5.67 2ω = 53.7 ° ～ 5.9 °
R 1 = 33.513 D 1 = 1.30 N 1 = 1.846660 ν 1 = 23.9
R 2 = 21.293 D 2 = 4.00 N 2 = 1.487490 ν 2 = 70.2
R 3 = -221.076 D 3 = 0.10
R 4 = 20.037 D 4 = 2.40 N 3 = 1.603112 ν 3 = 60.6
R 5 = 61.171 D 5 = variable
R 6 = 41.723 D 6 = 0.70 N 4 = 1.882997 ν 4 = 40.8
R 7 = 5.814 D 7 = 3.01
R 8 = -28.688 D 8 = 0.60 N 5 = 1.696797 ν 5 = 55.5
R 9 = 17.684 D 9 = 0.40
R10 = 10.908 D10 = 1.70 N 6 = 1.922860 ν 6 = 18.9
R11 = 33.976 D11 = variable
R12 = Aperture D12 = 0.50
R13 = 9.977 D13 = 2.00 N 7 = 1.693500 ν 7 = 53.2
R14 = -37.158 D14 = 3.51
R15 = 387.649 D15 = 0.60 N 8 = 1.846660 ν 8 = 23.9
R16 = 8.113 D16 = 0.29
R17 = 11.247 D17 = 2.10 N 9 = 1.603112 ν 9 = 60.6
R18 = -639.500 D18 = variable
R19 = 14.054 D19 = 0.70 N10 = 1.487490 ν10 = 70.2
R20 = 10.731 D20 = variable
R21 = 14.536 D21 = 2.90 N11 = 1.804000 ν11 = 46.6
R22 = -37.028 D22 = 0.60 N12 = 1.846660 ν12 = 23.9
R23 = -251.285 D23 = variable
R24 = ∞ D24 = 1.28 N13 = 1.516330 ν13 = 64.1
R25 = ∞

\ Focal length 6.61 26.05 64.78
Variable interval \
D 5 0.70 13.72 19.30
D11 21.03 6.60 1.43
D18 0.50 1.91 1.50
D20 6.92 2.43 9.60
D23 7.40 11.88 4.72

Aspheric coefficient
R14 k = -2.14372e + 02 B = -3.53656e-04 C = 3.48279e-05 D = -1.39789e-06
E = 0.00000e + 00

<Numerical Example 3>
f = 6.50-64.60 Fno = 3.61-5.67 2ω = 54.5 °-5.9 °
R 1 = 36.036 D 1 = 1.30 N 1 = 1.728250 ν 1 = 28.5
R 2 = 20.572 D 2 = 4.00 N 2 = 1.438750 ν 2 = 95.0
R 3 = -108.255 D 3 = 0.10
R 4 = 18.755 D 4 = 2.40 N 3 = 1.603112 ν 3 = 60.6
R 5 = 53.640 D 5 = Variable
R 6 = 46.108 D 6 = 0.70 N 4 = 1.882997 ν 4 = 40.8
R 7 = 6.024 D 7 = 2.73
R 8 = -41.506 D 8 = 0.60 N 5 = 1.696797 ν 5 = 55.5
R 9 = 17.655 D 9 = 0.40
R10 = 10.769 D10 = 1.50 N 6 = 1.922860 ν 6 = 18.9
R11 = 27.978 D11 = variable
R12 = Aperture D12 = 1.50
R13 = 10.777 D13 = 2.00 N 7 = 1.693500 ν 7 = 53.2
R14 = -37.304 D14 = 3.61
R15 = -58.658 D15 = 0.60 N 8 = 1.846660 ν 8 = 23.9
R16 = 8.738 D16 = 0.22
R17 = 11.175 D17 = 2.10 N 9 = 1.804000 ν 9 = 46.6
R18 = -17.983 D18 = variable
R19 = -18.910 D19 = 0.70 N10 = 1.487490 ν10 = 70.2
R20 = 9.648 D20 = variable
R21 = 14.324 D21 = 3.30 N11 = 1.804000 ν11 = 46.6
R22 = -11.012 D22 = 0.60 N12 = 1.846660 ν12 = 23.9
R23 = -30.531 D23 = variable
R24 = ∞ D24 = 1.28 N13 = 1.516330 ν13 = 64.1
R25 = ∞

\ Focal length 6.50 20.58 64.60
Variable interval \
D 5 0.70 9.82 19.70
D11 19.50 6.12 1.50
D18 1.50 5.76 0.50
D20 4.76 4.60 8.86
D23 7.65 7.80 3.54

Aspheric coefficient
R13 k = 7.20570e-01 B = 1.71220e-05 C = -7.85975e-06 D = 4.66646e-07
E = 0.00000e + 00
R14 k = -2.19192e + 02 B = -2.78497e-04 C = 2.94176e-05 D = -1.06973e-06
E = 0.00000e + 00

<Numerical Example 4>
f = 6.66 to 64.66 Fno = 3.61 to 5.67 2ω = 53.4 ° to 5.9 °
R 1 = 33.730 D 1 = 1.30 N 1 = 1.805181 ν 1 = 25.4
R 2 = 21.242 D 2 = 4.00 N 2 = 1.496999 ν 2 = 81.5
R 3 = -222.548 D 3 = 0.10
R 4 = 19.592 D 4 = 2.40 N 3 = 1.603112 ν 3 = 60.6
R 5 = 55.735 D 5 = variable
R 6 = 51.057 D 6 = 0.70 N 4 = 1.882997 ν 4 = 40.8
R 7 = 5.957 D 7 = 2.95
R 8 = -26.146 D 8 = 0.60 N 5 = 1.696797 ν 5 = 55.5
R 9 = 18.026 D 9 = 0.40
R10 = 11.320 D10 = 1.70 N 6 = 1.922860 ν 6 = 18.9
R11 = 35.176 D11 = variable
R12 = 10.850 D12 = 2.00 N 7 = 1.693500 ν 7 = 53.2
R13 = -36.094 D13 = 1.00
R14 = Aperture D14 = 2.50
R15 = 74.437 D15 = 0.60 N 8 = 1.846660 ν 8 = 23.9
R16 = 8.361 D16 = 0.23
R17 = 10.566 D17 = 2.10 N 9 = 1.603112 ν 9 = 60.6
R18 = -18.880 D18 = variable
R19 = -35.563 D19 = 0.70 N10 = 1.487490 ν10 = 70.2
R20 = 11.702 D20 = variable
R21 = 15.140 D21 = 2.90 N11 = 1.804000 ν11 = 46.6
R22 = -16.517 D22 = 0.60 N12 = 1.846660 ν12 = 23.9
R23 = -51.845 D23 = variable
R24 = ∞ D24 = 1.28 N13 = 1.516330 ν13 = 64.1
R25 = ∞

\ Focal length 6.66 24.48 64.66
Variable interval \
D 5 0.70 11.20 18.20
D11 20.15 5.81 0.65
D18 1.50 5.34 3.50
D20 6.75 3.20 8.79
D23 7.10 10.65 5.07

Aspheric coefficient
R13 k = -1.32894e + 02 B = -1.83375e-04 C = 1.72475e-05 D = -5.54298e-07
E = 0.00000e + 00

L1: First lens group L2: Second lens group L3: Third lens group L4: Fourth lens group L5: Fifth lens group SP: Aperture stop IP: Image plane d: d line g: g line C: C line F: F line ΔS: Sagittal image plane ΔM: Meridional image plane ω: Half angle of view

Claims (9)

In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a positive lens group The second lens group, the third lens group, and the fifth lens group move during zooming, and the first lens group and the fourth lens group are used for zooming. Is immobile
The first lens group includes a cemented lens obtained by cementing a negative lens and a positive lens in order from the object side to the image side, and a positive lens.
The third lens group includes two positive lenses and one negative lens,
The focal length of the fourth lens group is f4, the focal length of the entire system at the wide angle end is fw, the focal length of the negative lens constituting the third lens group is f3n, and the focal length of the third lens group is f3. When
1.0 <| f4 | / fw <17.0
0.4 <| f3n | / f3 <1.0
A zoom lens characterized by satisfying the following conditions: The lateral magnifications at the wide-angle end and the telephoto end of the second lens group are β2w and β2t, respectively, the lateral magnifications at the wide-angle end and the telephoto end of the third lens group are β3w and β3t, respectively, and the focal length of the entire system at the telephoto end is ft. And when
0.7 <(β2t / β2w) / (ft / fw) <2.0
0.01 <(β3t / β3w) / (ft / fw) <0.2
The zoom lens according to claim 1, wherein the following condition is satisfied. When the lateral magnification at the telephoto end of the third lens group is β3t, the lateral magnification at the telephoto end of the fourth lens group is β4t, and the lateral magnification at the telephoto end of the fifth lens group is β5t,
1.0 <(1-β3t) × β4t × β5t <2.0
The zoom lens according to claim 1, wherein the following condition is satisfied. The fourth lens group is composed of one negative lens, and when the radius of curvature of the object-side and image-side lens surfaces of the negative lens is R4a and R4b,
0.1 <(R4a + R4b) / (R4a-R4b) <8.0
The zoom lens according to claim 1, wherein the following condition is satisfied. The first lens group has a cemented lens composed of a positive lens and a negative lens, and when the Abbe number of the material of the positive lens constituting the cemented lens is νd1p and the partial dispersion ratio is θgF1p,
−0.0016νd1p + 0.641 <θgF1p
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the first lens group is f1, and the focal length of the second lens group is f2,
2.0 <f1 / fw <6.0
1.0 <| f2 | / fw <1.5
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the fifth lens group is f5,
1.5 <f3 / fw <3.0
1.5 <f5 / fw <3.0
The zoom lens according to claim 1, wherein the following condition is satisfied. The zoom lens according to claim 1, wherein an image is formed on a solid-state image sensor. An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image sensor that receives an image formed by the zoom lens.